Biomedical Engineering Reference
In-Depth Information
vector information. Pseudocode for the PDE-based and the greedy snake methods
are provided in this appendix:
A. Pseudocode for Snake Computation Using the PDE Approach
1.
Input image
I
(
x, y
)
2.
Preprocessing
(a)
Compute feature map (Input Image
I
)
i.
Compute gradient map G =
∇
G
σ
⊕
I
A.
Normalize G
ii.
Compute regional information-based normalized feature
map F
3.
Input discrete points
4.
Define a contour through the sample points on the curve
5.
Input parameter values for snake computation:
α
= strength of elas-
ticity;
β
= rigidity strength;
γ
= gradient strength;
η
= other factor
(might
be regional or user-defined constraints). The number of parameters
introduced will be equal to the number of force fields used.
6.
Define stiffness matrix
c
1
b
1
a
1
...
...
...
...
...
a
N−
1
b
N
b
1
c
2
b
2
a
2
...
...
...
...
0
a
N
a
1
b
2
c
3
b
3
a
3
...
...
...
0
0
0
a
2
b
3
c
4
b
4
a
4
...
...
...
...
...
...
...
...
...
...
...
...
...
...
K
=
,
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
0
0
...
...
...
a
N−
4
b
N−
3
c
N−
2
b
N−
2
a
N−
2
a
N−
1
0
...
...
...
0
a
N−
3
b
N−
2
c
N−
1
b
N−
1
b
N
a
N
...
...
...
0
0
a
N−
2
b
N−
1
c
N
h
4
a
i
=
β
i
+1
,
h
4
b
i
=
−
2
β
i
−
2
β
i
+1
−
h
2
α
i
+1
,
h
4
c
i
=
β
i−
1
+4
β
i
+
β
i
+1
+
h
2
α
i
+
h
2
α
i
+1
,
where
α
,
β
are the coefficient values.
1.
While (Iterations
=
Maximum Iterations)
